Design of a 60.8 K superconducting hydride LiMgZr2H12 at ambient pressure via Lithium doping
School of Physics, Xidian University（西安电子科技大学物理学院）；College of Physics and Optoelectronic Technology, Baoji University of Arts and Sciences（宝鸡文理学院物理与光电技术学院）
High-pressure hydrogen-rich compounds have long been regarded as promising room-temperature superconductor candidates; however, their practical applications are limited by their reliance on extreme compression. This study explores hydrogen-rich superconductors that may be stable at ambient pressures. Inspired by recent investigations of the MgZrH2n family, the LiMgZr2H12 structure with a Pmmm symmetry was constructed, and its thermodynamic, mechanical, and dynamical stability were evaluated using first-principles calculations. Electron-phonon coupling (EPC) analysis suggests that LiMgZr2H12 reaches a superconducting critical temperature (Tc) of 60.8 K at ambient pressure. Compared with MgZrH6, Li doping significantly increases the contribution of hydrogen atoms to the electron density of states near the Fermi level (EF) and enhances the EPC constant of the LiMgZr2H12 structure. LiMgZr2H12 exhibits a superconducting figure of merit of 1.56, which is significantly greater than that of MgZrH6, demonstrating its outstanding potential for practical applications. This work guides ambient-pressure design of high-Tc hydrides.
Over the past decade, a combination of crystal structure prediction techniques and experimental synthetic work has thoroughly explored the phase diagrams of binary hydrides under pressure. The fruitfulness of this dual approach is demonstrated in the recent identification of several superconducting hydrides with $T_c$s approaching room temperature. We start with an overview of the computational procedures for predicting stable structures and estimating their propensity for superconductivity. A survey of phases with high $T_c$ reveals some common structural features that appear conducive to the…
Reaching superconductivity at ambient conditions is one of the biggest scientific dreams. The discoveries in the last few years at high pressures place hydrogen-based compounds as the best candidates for making it true. As the recent history shows, first-principles calculations are expected to continue guiding the experimental quest in the right track in the coming years. Considering that ionic quantum fluctuations largely affect the structural and vibrational properties of superconducting hydrides, in many cases making them stable at much lower pressures than expected, it will be crucial to i…
Search for thermodynamically stable ambient-pressure superconducting hydrides in GNoME database
Max-Planck-Institut für Mikrostrukturphysik（马克斯·普朗克微结构物理研究所）；Martin-Luther-Universität Halle-Wittenberg（马丁·路德·哈勒-维滕贝格大学）；University of Coimbra（科英布拉大学）；Periodic Labs（周期实验室）；University of the Basque Country (UPV/EHU)（巴斯克大学）；Centro de Física de Materiales (CFM-MPC), CSIC-UPV/EHU（材料物理中心，西班牙国家研究委员会-巴斯克大学）；Donostia International Physics Center (DIPC)（圣塞巴斯蒂安国际物理中心）
We report the observation of conventional superconductivity at the highest temperature yet attained without mechanical compression, around 54 kelvin in palladium-hydride and 60 kelvin in palladium-deuteride. The remarkable increase in Tc compared to the previously known value was achieved by rapidly cooling the hydride and deuteride after loading with hydrogen or deuterium at elevated temperature. Our results encourage hope that conventional superconductivity under ambient conditions will be discovered in materials with very high hydrogen density, as predicted more than a decade ago.
Searching for superconducting hydrides has so far largely focused on finding materials exhibiting the highest possible critical temperatures ($T_c$). This has led to a bias towards materials stabilised at very high pressures, which introduces a number of technical difficulties in experiment. Here we apply machine learning methods in an effort to identify superconducting hydrides which can operate closer to ambient conditions. The output of these models informs structure searches, from which we identify and screen stable candidates before performing electron-phonon calculations to obtain $T_c$.…
Binary hydrides formed by the pnictogens of phosphorus, arsenic and antimony are studied at high pressures using first principles methods. Stable structures are predicted and their electronic, vibrational and superconducting properties are investigated. We predict that SbH$_{4}$ and AsH$_{8}$ will be high-temperature superconductors at megabar pressures, with critical temperatures in excess of 100 K. The highly symmetric hexagonal SbH$_{4}$ phase is predicted to be stabilized above about 150 GPa, which is readily achievable in diamond anvil cell experiments. We find that all phosphorus hydride…
Ambient and Pressure Dependent Superconductivity with Hydrogen Storage Potential in Quaternary Hydride LiMgZr2H12: A Comprehensive First-principles Insights
Department of Physics, University of Rajshahi（拉杰沙希大学物理系）
The discovery of a record high superconducting transition temperature (Tc) of 288 K in a pressurized hydride inspires new hope to realize ambient condition superconductivity. Here, we give a perspective on the theoretical and experimental studies of hydride superconductivity. Predictions based on the BCS-Eliashberg-Midgal theory with the aid of density functional theory have been playing a leading role in the research and guiding the experimental realizations. To date, about twenty hydrides experiments have been reported to exhibit high-Tc superconductivity and their Tc agree well with the pre…
To raise the superconducting-transition temperature (Tc) has been the driving force for the long, sustained effort in superconductivity research. Recent progress in hydrides with Tcs up to 287 K under 267 GPa has heralded a new era of room-temperature superconductivity (RTS) with immense technological promise. Indeed, RTS has lifted the temperature barrier for the ubiquitous application of superconductivity. Unfortunately, formidable pressure is required to attain such high Tcs. The most effective relief to this impasse is to remove the pressure needed while retaining the pressure-induced Tc w…
In the last five years a large number of new high-temperature superconductors have been predicted and experimentally discovered among hydrogen-rich crystals, at pressures which are way too high to meet any practical application. In this work, we report the computational prediction of a hydride superconductor, LaBH$_{8}$, with a T$_{c}$ of 126 K at a pressure of 50 GPa, thermodynamically stable above 100 GPa, and dynamically stable down to 40 GPa, an unprecedentedly low pressure for high-T$_{c}$ hydrides. LaBH$_{8}$ can be seen as a ternary sodalite-like hydride, in which a metallic hydrogen su…
The maximum critical temperature for superconductivity in pressurized hydrides appears at the top of superconducting domes in Tc versus pressure curves at a particular pressure, which is not predicted by standard superconductivity theories. The a high-order anisotropic van Hove singularity near the Fermi level observed in band structure calculations of pressurized sulfur hydride, typical of a supermetal, has been associated with the array of metallic hydrogen wires modules forming a nanoscale heterostructure at atomic limit called superstripes phase. Here we propose that pressurized sulfur hyd…
Noble metals adopt close-packed structures at ambient pressure and rarely undergo structural transformation at high pressures. Platinum (Pt), in particular, is normally considered to be unreactive and is therefore not expected to form hydrides under pressure. We predict that platinum hydride (PtH) has a lower enthalpy than its constituents solid Pt and molecular hydrogen at pressures above 21.5 GPa. We have calculated structural phase transitions from tetragonal to hexagonal close-packed or face-centered cubic (fcc) PtH between 70 and 80 GPa. Linear response calculations indicate that PtH is a…
We investigate the superconducting ternary lithium borohydride phase diagram at pressures of 0 and 200$\,$GPa using methods for evolutionary crystal structure prediction and linear-response calculations for the electron-phonon coupling. Our calculations show that the ground state phase at ambient pressure, LiBH$_4$, stays in the $Pnma$ space group and remains a wide band-gap insulator at all pressures investigated. Other phases along the 1:1:$x$ Li:B:H line are also insulating. However, a full search of the ternary phase diagram at 200$\,$GPa revealed a metallic Li$_2$BH$_6$ phase, which is th…
Fermi velocity, $v_F$, is one of the primary characteristics of any conductor, including superconductors. For conductors at ambient pressure several experimental techniques have been developed to measure $v_F$ and, for instance, Zhou et al (Nature 423 398 (2003)) reported that high-Tc cuprates exhibit universal nodal Fermi velocity of $v_F$ = $2.7*10^5$ m/s. However, there were no experimental techniques applied to measure $v_F$ in highly-compressed near-room-temperature superconductors (NRTS), due to experimental challenges. Here to answer a question about the existence of the universal Fermi…
We predicted a new ternary hydride Li$_2$SiH$_6$ at high pressures. A systematic structure search in Li$_2$SiH$_6$ compound reveals novel stable phases with intriguing electronic and phonon properties. It is found that Li$_2$SiH$_6$ is dynamically stable from ambient pressure up to 400 GPa with three novel phases: P312, P$\bar{3}$, and P$\bar{6}$2m. The calculation of electron-phonon coupling combined with Bardeen-Cooper-Schrieffer's argument indicates that this compound may be a candidate for high $T_c$ superconductors under high pressures. In particular, the maximum $T_c$ of $P\bar{6}2m$-Li$…
Hydrogen-based superconductors provide a route to the long-sought goal of room-temperature superconductivity, but the high pressures required to metallize these materials limit their immediate application. For example, carbonaceous sulfur hydride, the first room-temperature superconductor, can reach a critical temperature (Tc) of 288 K only at the extreme pressure of 267 GPa. The next recognized challenge is the realization of room-temperature superconductivity at significantly lower pressures. Here, we propose a strategy for the rational design of high-temperature superconductors at low press…
Motivated by the recent report of superconductivity above 200 K in ultra-dense hydrogen sulfide, we search for high-\tc\ conventional superconductivity in the phase diagram of the binary Li-S system, using {\em ab-initio} methods for crystal structure prediction and linear response calculations for the electron-phonon coupling. We find that at pressures higher than 20 GPa, several new compositions, besides the known Li$_2$S, are stabilized; many exhibit electride-like {\em interstitial} charge localization observed in other alkali metal compounds. Of all predicted phases, only Li$_3$S at P > 6…
We investigate the possibility of achieving high-temperature superconductivity in hydrides under pressure by inducing metallization of otherwise insulating phases through doping, a path previously used to render standard semiconductors superconducting at ambient pressure. Following this idea, we study H$_2$O, one of the most abundant and well-studied substances, we identify nitrogen as the most likely and promising substitution/dopant. We show that for realistic levels of doping of a few percent, the phase X of ice becomes superconducting with a critical temperature of about 60 K at 150GPa. In…
The discovery of superconductivity at 203 K in H3S brought attention back to conventional superconductors whose properties can be described by the Bardeen-Cooper-Schrieffer (BCS) and the Migdal-Eliashberg theories. These theories predict that high, and even room temperature superconductivity (RTSC) is possible in metals possessing certain favorable parameters such as lattice vibrations at high frequencies. However, these general theories do not suffice to predict real superconductors. New superconducting materials can be predicted now with the aid of first principles calculations based on Dens…
Disentangling electronic and phononic contributions to high-temperature superconductivity in X2MH6 hydrides
Jimei University（集美大学）；Xiamen University（厦门大学）；Iowa State University（爱荷华州立大学）；Guangdong University of Technology（广东工业大学）；Ames National Laboratory, U.S. Department of Energy（美国能源部艾姆斯国家实验室）
The extreme pressures required to stabilize the recently discovered superhydrides represent a major obstacle to their practical application. In this paper, we propose a novel route to attain high-temperature superconductivity in hydrides at ambient pressure, by doping commercial metal borohydrides. Using first-principles calculations based on Density Functional Theory and Migdal-Eliashberg theory, we demonstrate that in Ca(BH$_4$)$_2$ a moderate hole doping of 0.03 holes per formula unit, obtained through a partial replacement of Ca with monovalent K, is sufficient to achieve $T_c$'s as high a…
Experimental discovery that compressed sulphur hydride exhibits superconducting transition temperature Tc=203 K (Drozdov et al 2015 Nature 525 73) sparked intensive studies of superconducting hydrides. However, this discovery was not a straight forward experimental examination of theoretically predicted phase, instead it was nearly five-decade long experimental quest for superconductivity in highly-compressed matters, which varied from pure elements (hydrogen, oxygen, sulphur, lithium), cuprates, and hydrides (SiH4, YH3, and AlH3), to semiconductors and ionic salts. One of these salts was cesi…
Superconductivity up to 17 K in the high-pressure rhombohedral-I phase of ReO3: a potential oxide analogy of hydride superconductors
Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences（中国科学院物理研究所）；School of Physical Sciences, University of Chinese Academy of Sciences（中国科学院大学物理科学学院）；Faculty of Science, Wuhan University of Science and Technology（武汉科技大学理学院）；Key Laboratory of Materials Physics, Ministry of Education, School of Physics and Microelectronics, Zhengzhou University（郑州大学物理与微电子学院材料物理教育部重点实验室）；Institute for Solid State Physics, University of Tokyo（东京大学固体物理学研究所）
